This invention relates to a method of feeding ruminant animals. One aspect of the invention relates to more efficient utilization of protein-containing feeds for ruminant animals. Another aspect of this invention relates to a method of feeding ruminant animals proteinaceous feeds and feed supplements that resist biodegradation in the rumen portion of the ruminant animal's stomach but can be digested in the abomasum and lower gut. A further aspect of this invention relates to a method of feeding ruminant animals whereby it is possible to achieve increased growth rates and milk production.
The rumen or first stomach of a ruminant animal is the site of microbial digestion of forage cellulose. Microbial protein synthesized in the rumen during this process then becomes a major source of protein reaching the post-rumen gut. Unfortunately, rumen microflora such as bacteria and protozoa rapidly degrade the protein and amino acids which are present in the diet fed to the ruminant animal and are soluble in the rumen liquid phase. W. Chalupa, in his article "Rumen Bypass and Protection of Proteins and Amino Acids", 58 JOURNAL OR DAIRY SCIENCE 1198 (1975), cites the conclusions of several researchers that as little as 40% or as much as 80% of the dietary protein might be degraded in the rumen and transferred into microprotein. A further portion of the nitrogen produced by deamination of dietary protein by rumen microbes is not utilized for the synthesis of microbial protein, but is lost as ammonia either in belched rumen gases or absorbed through the rumen wall and ultimately excreted.
Therefore, while the rumen endows the ruminant animal with the capacity to digest and utilize cellulose effectively, it is relatively inefficient in the digestion and utilization of dietary protein contained in feed supplements. This explains the commonly accepted commercial practice of regulating the protein content of ruminant animals' diets to carefully predetermined levels. Protein fed in excess of these commercially accepted amounts usually does not improve animal growth or milk production.
The science of rumen bypass of feed proteins has been the subject of numerous investigations and subsequent literary reports. In his article, "Lactational Responses to Postruminal Administration of Proteins and Amino Acids", 58 JOURNAL OF DAIRY SCIENCE, 1178 (1975), J. H. Clark concluded that, "Future research to delineate limiting nutrients for post-ruminant supplementation should prove fruitful and should make a major contribution to improved production by ruminant animals." Similarly, W. Chalupa, supra, stated: "A feasible approach to production of animal protein from ruminants would be . . . maximization of rumen by-pass of dietary proteins and supplementation with rumen nondegradable amino acids." The importance of rumen bypass is illustrated by results of research trials where a high quality protein such as casein has been infused directly into the post-ruminal digestive tract of lactating dairy cows. Commenting upon these trials, Clark noted in his article that post-ruminal supplementation of casein has increased milk production from 1 to 4 kg/cow/day and milk protein yield by 10% to 15%. He also observed that the greatest increase in milk yield came from the highest producing cows.
Various methods have been utilized to protect proteins from rumen degradation. The two most commonly researched methods involve the denaturation of protein either by heat treatment or by chemical treatment with formaldehyde. The heat denaturation method was addressed by the Chalupa articles, and by K. Ferguson in "Microbial Fermentation in the Rumen", IV INTERNATIONAL SYMPOSIUM ON RUMINANT PHYSIOLOGY 448 (1974). Chalupa and Ferguson believe that reduced microbial fermentation as a consequence of heat treatment is attributable to the Maillard reaction between sugar aldehyde groups and free amino groups, and condensation reactions between the E-amino group of lysine and other amino acid side chains. Chalupa reviews many examples where rumen protection has been increased by heat treatment leading to increased nitrogen retention, weight gain and feed efficiency. However, protection produced by heating is counterbalanced by decreases in digestibility and biological value.
The treatment of proteinaceous matter with an aldehyde is disclosed in U.S. Pat. No. 3,619,200 to Ferguson. The protection of protein by treatment with formaldehyde has led to variable results. Chalupa states that in experiments with sheep, treatment of casein with formaldehyde generally has resulted in increased nitrogen retention, and wool and muscle growth, while treatment of plant proteins has not yielded consistent results. Formaldehyde treatment of soymeal and casein has not led to increased milk production in dairy cows. Furthermore, treatment of protein with formaldehyde usually leads to decreased protein digestibility.
An effective method of feeding ruminant animals so as to achieve rumen bypass for a wide variety of feed proteins is needed. Bypassing protein digestion in the rumen will result in increased milk production similar to that obtained by infusing high quality protein directly into the post-ruminal digestive tract. Furthermore, a method of feeding so as to achieve rumen bypass will increase the growth rate of ruminant animals.